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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/99156] __builtin_expect is folded too soon allowing an non-integer-constant-expr to become an integer-const-expr
Date: Fri, 23 Jul 2021 18:18:42 +0000	[thread overview]
Message-ID: <bug-99156-4-CYMPNfC4pr@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-99156-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99156

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|__builtin_expect affects    |__builtin_expect is folded
                   |the interpretation of its   |too soon allowing an
                   |first operand               |non-integer-constant-expr
                   |                            |to become an
                   |                            |integer-const-expr
                 CC|                            |pinskia at gcc dot gnu.org

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Here is another example which shows the problem even further:
int maybe_vla(int n) {
    goto label;
    int arr[__builtin_expect(n-n, 0)];
label:
    return sizeof(arr);
}

int main() { return maybe_vla(0); }

---- CUT ----
Basically __builtin_expect is folded too soon which allows the argument to be
considered a constant integer expression :).

      parent reply	other threads:[~2021-07-23 18:18 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-19  4:29 [Bug c/99156] New: __builtin_expect affects the interpretation of its first operand zhan3299 at purdue dot edu
2021-02-19 15:15 ` [Bug c/99156] " marxin at gcc dot gnu.org
2021-02-19 21:32 ` zhan3299 at purdue dot edu
2021-07-23 18:18 ` pinskia at gcc dot gnu.org [this message]

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